Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Class-Based Fair Code Allocation with Delay Guarantees for OVSF-CDMA and VSF-OFCDM in Next-Generation Cellular Networks | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2010 Article ID 738325 21 pages doi 2010 738325 Research Article Class-Based Fair Code Allocation with Delay Guarantees for OVSF-CDMA and VSF-OFCDM in Next-Generation Cellular Networks Narasimha Challa and Hasan Cam Computer Science and Engineering Department Arizona State University Tempe AZ 85287 USA Correspondence should be addressed to Hasan Cam Received 12 June 2010 Revised 30 September 2010 Accepted 15 November 2010 Academic Editor Yuh Shyan Chen Copyright 2010 N. ChallaandH. Cam. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. This paper presents a novel class-based fair code allocation CFCA protocol to support delay and rate guarantees for realtime flows and to provide fairness for non-real-time flows on the downlink of WCDMA- and VSF-OFCDM-based cellular networks. CFCA not only assigns bandwidth dynamically to different flows but also determines those appropriate OVSF codes whose assignment results in the minimum overhead for code reassignments during dynamic bandwidth allocation. To reduce the overhead of code reassignments this paper introduces the concept of affinity-mate and enables bandwidth allocation and code placement to interact with each other. A new performance metric called class-based rate degradation ratio CRD is introduced to ensure fairness in providing rate and delay guarantees by measuring the rate degradations of flows based on their traffic types. The simulation results show that code reassignment overhead can be reduced by up to 60 for high network loads. For low network loads fairness is achieved fully but for high network loads the average rate requirement is met fairly for 95 of the flows. 1. Introduction In cellular networks limited radio spectrum is a
